“The Purge: Anarchy” has emerged as the wild card in a too-close-to-call weekend box office race between the low-budget horror thriller, the Cameron Diaz-Jason Segel comedy “Sex Tape” and reigning champ “Dawn of the Planet of the Apes.”

Both “Anarchy” and “Apes” will wind up in the $30 million range for the three days, and “Sex Tape” shouldn’t be far behind, say analysts. “Apes” looks to have a slight advantage based on its very strong — $8.2 million Monday and $9.6 million Tuesday — midweek showings. Also opening wide is Disney’s animated sequel “Planes: Fire and Rescue,” which is projected to land with around $20 million.

You can make a case for all three of the front-runners.

“Anarchy” is a sequel to “The Purge,” the micro-budget home invasion tale that opened to a stunning $34.1 million last June. Universal’s marketing team did a great job selling the high-concept tale of a single dangerous night when laws don’t apply, all the more impressive given the film’s $3 million price tag.

“Anarchy” cost a little more, but at $9 million the threshold for profitability remains very low. And the studio seems to have generated considerable heat around the sequel — no small feat, since critics skewered the original (34 percent positive on Rotten Tomatoes) and audiences did too, with a crummy “C” CinemaScore. Despite all that, it wound up taking in nearly $90 million worldwide, which is why we’re seeing a sequel.

The social media signs are strong, and it has more than 2.1 million “likes” on Facebook, four times that of the first film. But it’s worth noting that this has been a tough stretch for horror movies — not one has opened over $20 million since last September’s “Insidious 2.”

“This one’s really more of a thriller,” Universal distribution chief Nikki Rocco told TheWrap. It will be in 3,303 theaters.

Sony’s “Sex Tape” is the latest R-rated comedy in a summer that has seen plenty of them. But the prospects look good for this reunion of “Bad Teacher” principals Diaz, Segel and director Jake Kasdan. That one took in $216 million worldwide for the studio after opening to $31.6 million in June of 2011.

The screenplay is by Kate Angelo and Nicholas Stoller and Segel. Todd Black, Jason Blumenthal and Steve Tisch produced the $40 million comedy from MRC and LStar Capital and Escape Artists Production. David Householter, David Bloomfield and Ben Waisbren executive produce, along with Kasdan and Segel.

It’s doing OK on social media, but is behind where “Neighbors” was on both Facebook and Twitter at a similar stage. That’s likely an indicator that “Sex Tape” will play to an older crowd. It will be in 3,060 theaters.

Fox’s “Planet of the Apes” is looking to become the second of summer’s No. 1 movies to repeat as champ, following “Transformers: Age of Extinction.” It’s up to more than $90 million domestically and $123 million worldwide in five days.

The reviews and word of mouth have been very strong, so a drop in the 55 percent range from its $72.6 million debut is possible. That would put it a little over $32 million, which might be enough to take the weekend.

Advance sales at online ticket broker Fandango show “Apes” leading, with “The Purge: Anarchy” not far behind and pacing ahead of the original film and last summer’s horror hit “The Conjuring.”

“Planes: Fire and Rescue,” the PG-rated animated film from Disney Toon Studios, will roll out on roughly 3,600 theaters.

It’s is a spinoff of the “Cars” franchise. The original brought in $244 million domestically and $461 million worldwide in 2006. “Cars 2” took a in 2011 with $191 million in the U.S. but brought in $560 million worldwide. Those were both moneymakers for Disney, and since this one has a modest $50 million production budget, it should be too.